1. Field of the Invention
The present invention relates to a method for estimating location of a moving object in a navigation system, which is capable of accurately estimating a next location of the object by using a speed of the moving object and a direction of the link on a digital numeric map especially when a moving object (e.g. a vehicle) goes in a shadow area.
2. Description of the Related Art
Generally, in the navigation system, location information of the moving object is provided continuously in real time within a range of an allowable error and used for the services to display the present location of the moving object, to guide a moving path and to recognize an environment. However, the wrong location estimation or the discontinuous location estimation can affect a movement of the moving object seriously. Therefore, it is very important to estimate the location of the moving object.
The method for estimating the location of the moving object is disclosed in the Korean Patent No. 216535 (Application No. 1997-24564).
According to the Korean Patent No. 216535, the present location of the moving object is found in a dead reckoning (DR) technique by using data collected from a direction and distant sensor attached to the moving object and set to be a first moving location. Correction is performed on the link on the digital numeric map by a map mapping method using a location matching of the first moving location and the corrected position is set to be a second moving location. The present location of the moving object is estimated using the GPS location information received from GPS and set to be a third moving location. Correction is performed on the link on the digital numeric map by a map mapping method using a location matching and the third moving location is set to be a fourth moving location. Short distance moving patterns of the first to fourth moving locations are found, and similarities representing how much the short distance moving patterns of the first to fourth moving locations are matched with the link pattern are compared with each other. The moving location having the highest similarity is estimated as the final present location.
In such a location estimation method, the location of the moving object is estimated using a sensor signal and a GPS location data by the dead reckoning technique.
Without using the dead reckoning technique, direction sensors such as a gyro and an electronic compass may have errors depending on rotation direction. Traveling direction can be deflected or changed when the moving object stops. Therefore, the estimated traveling direction can include an error. Estimation of moving distance by wheel sensors includes errors due to external elements such as air pressure and street conditions. Accordingly, it is very difficult to solve instability of location estimation and to provide navigation service such as a map mapping in GPS shadow areas in the navigation system without any direction sensor.
It is not easy to estimate the locations of the moving object such as a mobile telephone having no direction sensors such as a gyro and an electronic compass, and the moving objects in the shadow areas, in which GPS data are not received, and the unreliable regions such as tunnel and underground passage in which quality of the received GPS location data is greatly lowered though the GPS location data is received. It is very difficult to estimate the location of the moving object precisely due to errors caused during estimation even if the location of the moving object can be estimated.